carbs again again

[johnfrenchsr]

I have rebuilt them put in 140 jets and new intake boots and new plugs. I have checked for leaks with starter fluid no leaks. I purchased some guages from J. C. Witby. the best I can get them to sync is 10 on 1&2 and 5 on 3&4. When I start to sync 1&2 the rpms go to 4000. Is it possible one of the diaphram is leaking causing it not to sync.It is runing good with good throttle.So should I just not worry about it. Is there anywhere I can get a new minuki carb that will fit a xs.

[xj11john]

synching carbs

I'm sure you synch your carbs per the carb synching tech tip, but just to reiterate that #3 is the one all the rest have to be synched to .

First sync carb #1 to #2 from above using the silver, slotted screw on the throttle linkage, halfway between the manifold for the two carbs (carbs #1 & #2). Turn the screw until the mercury columns for carbs #1 & #2 are even (within 1 cm). The adjusting screw will change the reading in one of the two columns - the goal isn't to get the columns to some specific height, it's to get them all even.

Next sync carb #4 to #3 using the screw between the carbs #3 & #4.

Finally, use the screw between carbs #2 and #3 to bring the two pairs of carbs (#1-#2 and #3-#4) into sync. NOTE: Carb #3 cannot be changed, all other carbs must be synced to it.

[xj11john]

May be a vacuum leak

That may be your problem, so pull your carbs back down and check your diaphrams on 1 and 2 (oh heck maybe check them all)
and see if there are pinholes-if so there is a tech tip on using a rubber spray (not sure of the name of it) to repair them, maybe solve your rpm going up problem as your synch. Good luck.

[pggg]

Johnf, the l/h adjuster OPENS No1. The r/h adjuster OPENS No4. The middle adjuster OPENS No2. The rear idle screw OPENS No3.(along with all others) When you're tweaking the l/h adjuster, No 1 is opening too wide and revving high. Turn the adjuster ANTICLOCKWISE. If all carbs are pre-synced by eye or feeler gauge, things are easier to start with.

[turbopete]

That's what I do - pre-synch the throttles by removing the slides and adjust them by visually checking under the blades and getting the little crescent of light the same on each one.

[Ken Talbot]

Here's some illustration of how this works. Note in this detail shot how adjusting the screw will open or close the butterfly in one carb in relation to one other. The tab in the middle stays still, and the combination of screw on top and spring underneath moves the shaft for the next carb:


There are three adjusting screws - one between #1&2, one between #3&4, then the left-right screw between #2&3 :


Finally, the idle adjustment screw is the thumb wheel down under, between #2&3


It is quite normal to have the idle climb while you're doing a sync. Each time it does, set it back down to 800 or so before you continue. When you've got all the columns at the same height or as close as possible, then you can bring the idle up a bit to suit your own preference.

[pggg]

Also if you're using dial type vac gauges, have adjustable dampers(fishtank air taps or suchlike) inserted inline on each hose, then tweak the dampers so each gauge needle flickers with only 2 to 3 mm of movement.